You know it is communicating since it syncs, which is good. From the sound of things it seems the sensors are acting wonky. If a battery drain or reset/shutdown doesn't fix it, it may be more time for drastic measures like a factory reset, which to me that is always a last ditch effort to fix something. If you do decide to do a reset understand it may either fix everything or turn your watches into landfill fodder.
If you do decide on a factory reset I suggest you should first delete the watch from the Fitbit app, unpair it with your phones bluetooth, and if it was me I would uninstall the Fitbit app on my phone to be sure the data is gone (it will be saved in the Fitbit cloud), then finally do the watch factory reset. You will have to re-pair you watch as if it was new, but it should (fingers crossed) do the trick. If not, I have no further pixie dust to help, sorry.
It's your choice, but wanted to make sure you understand the risks. I know you have already gone through the settings, but if it was me I would go through things very slowly just to be sure. I've missed things in the past myself. I would also try powering off the watch completely to see if that makes a difference, then let the battery drain if not.
From a different thread, you can try what finally worked for this user Fitbit finally working correctly again
Good luck with it!
